In recent years, in order to reduce environmental load, a power generation system utilizing natural energy such as solar power generation, which does not emit carbon dioxide, is spreading into homes. However, upon power outage, power generation using natural energy represented by solar power generation can only output the maximum power of 1500 W from a self-sustained operation outlet provided in advance in a power conversion device. In addition, in order to cope with power shortage or the like after Great East Japan Earthquake, a system having a storage battery, a system using an electric automobile as a storage battery, a system combining solar power generation and a storage battery, and the like are being developed.
For example, Patent Document 1 indicated below discloses an operation method for distributed power supplies in the case where, upon power outage, a plurality of solar power generators and a plurality of storage batteries are operated in parallel in a coordinated manner to supply power to an electric light line released from a system.
That is, the following method is described. In the case where a plurality of distributed power supplies that are released from a power supply are operated in a self-sustained manner in parallel, one of the distributed power supplies is set as an AC voltage source for self-sustained operation, the other distributed power supplies are set as AC current sources synchronized with the AC voltage source, and thus these distributed power supplies are operated in a coordinated manner. In this case, the distributed power supplies operated as AC current sources are classified into a first distributed power supply having a storage battery and a second distributed power supply using natural energy but not having a storage battery. The second distributed power supply is controlled so as to track the maximum power point, and is configured to be able to supply surplus power to the first distributed power supply, and thus control is performed so as to perform the charging when surplus power is generated.
Patent Document 2 indicated below describes a configuration method for a parallel operation device, in which the AC voltage amplitude of a main power supply is set to be greater than that of a sub power supply, and output of an AC power supply is subjected to wired OR with diodes, using a switch, whereby, if the main power supply has no abnormality, power is supplied from only the main power supply, and if the main power supply has abnormality, the main power supply is automatically switched to the sub power supply.